Fuel or other types of tanks containing hazardous fluids often do not have check valves to prevent the unwanted exit of the fluids out of the tank. Rather, these tanks merely have grommets seated in the tank opening through which a filler pipe is inserted or have the filler pipe mounted directly to the tank.
It has been estimated that over half of the fires occurring in vehicle collisions are caused by fuel leaking out of the tank through the filler opening. Such leaks occur when the cap on the pipe is pried off or the pipe is forcibly drawn out of the grommet or the pipe is pulled off of the tank body. In all of the above instances, no barrier exists to block the path of the fuel out of the tank. As a result, it is highly likely that in a collision or other mishap fuel will leak out. Of course, the danger is equally as great if other types of hazardous fluids are contained in the tank. Should fuel be in the tank, leakage might lead to a fire that would seriously or fatally injure the occupants of the vehicle containing the tank.
Elastic check valves that permit fluid to flow in one direction but not in the reverse are well known in the art. Examples of U.S. patents on such check valves include U.S. Pat. Nos. 2,465,628; 2,986,098; 3,298,370; 3,361,161; 3,465,595; and 3,780,757. Yet, as was indicated earlier, check valves are not commonly included in tanks for hazardous fluids, especially vehicle fuel tanks. As a result, vehicle fires occur when fuel leaks from the tank. Thus, it is desirable to add to fuel and other types of tanks check valves, which are located inside the tank, to prevent dangerous leaks in the event the filler pipe or cap is removed unintentionally.
In addition, when attempting to retrofit fuel or other tanks with check valves, it also is desirable to provide valves which easily adapt to existing structures. Irregardless of the intended application, the check valve should be inexpensive to manufacture, easy to install and replace, and durable. Moreover, the valve should contain few moving parts to minimize the possibility of mechanical breakdown.